Method and apparatus for cutting tire tread stock



Jan. 23, 1951 v. s. FIRESTQNE METHOD AND APPARATUS FOR CUTTING TIRE TREAD STOCK Filed March 51, 1948 5 Sheets-Sheet l Jan. 23, 1951 v. s. FIREsToNE 2,539,240

METHOD AND APPARATUS FOR CUTTING TIRE TREAD STOCK Filed March 3l, 1948 5 Sheets-Sheet 2 Jan. 23, 1951 v. s. FIRESTONE` 2,539,240

METHOD AND APPARATUS FOR CUTTING TIRE TREAD STOCKv Filed MaICh 3.1, 1948 5 Sheets-Sheet 5 FIG. 5.

Jan. 23, 1951 v. s. FIREsToNE 2,539,240

METHOD AND IAPPARATUS'FOR CUTTING TIRE TREAD STOCK Y Filed March 5l, 1948 5 Sheets-Sheet 4 T1 7 y G 45 47 f5 HH m 55. /76

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Jan. 23, 1951 l v. s. FIREsToNE METHOD AND APPARATUS `FOR CUTTING TIRE TREAD STOCK 5 lSheecs-Shee'c 5 Filed March 3l, 1948 F1 G ll.

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Patented Jan. 23, y 1951 UNITED STATES PATENT i FiF 2,539,240 'METHOD Ami APPARArUsroe CUTTING TIRE vTREAD STOCK Vance 'S. Firestone, Newark, Ollio, fass'ignolg `f-by `mesn-e assignments, to Carlisle Corporation, Carlisle, Pa., -a corp'orationof l.Delaware Application "March 31, 1948,*Serial' No. `18;266

The presentinvention deals with `methods and apparatus for cutting iiexible 'sheet stock,!and has particular 'reference 'to improved methods andzapparatus Y for i cutting 'rubber tire tread fstock into tread-formingstri'ps of predetermined length.

fIn lthe past, considerable difficulty has been encountered when attemptingto cut uncuredf'rel- -1 'atively heavy, resilientand partially Ytacky rubber or synthetic rubber strips-or `sheets used to formthetreadr-portion of pneumatic'tires, due-to Ithe lrelative yieldable-lproperties of the tread stock, Yand itstendency to crumble and adherefto a knife bladedurin'glcutting operations. Various attemptshave beenfmade to overcome 'these obf-iectionable tendencies: and characteristics of the tread-stockin resisting fclean cutting, such as-lby carrying 4outethe-cuttin'g operations under Water, or under liquidspray, or, as-outlined in my pre- -vious United States `Patent No. 2,181,398, dated November 28, 1939,by-cuttingthe stockA on a Abias by 1means of-a highe'speed 'rotary knife. While v'these 'attempts have, to `some extent, vovercome the objectionable characteristics above mentioned,- no entirelyrsatis'factory @method crapparatus has heretofore been vrcommercially Used, whereby 'tire .'tread'stockV 'could rbey out .'efliciently and cleanly withoutra certain amount .of material building up `on the knifeio'r other vcutting in strumentality, thereby necessitating the inter mittent-shut-downf of lthe A'apparatus -for clean-ing purposes, or without vjagged or `uneven ,severance lines being obtained within the tread-forming stri-ps.

It follows lthereforeythatthe vprima-ry object of this invention Sis to 1 provide improved l methods andiapparatus Vfor, lefliciently and cleanly severing relatively flexible sheet stock into strips vof predeterminedvlengths, which `methods and .apparatuszlend themselves tosubstantially continuous :high speed operations.

It is anotherobject ofthis invention to provide a .machine forfcuttingftire tread stock which embodies apair `of 'vacuumlhold-down plates interposed `within a conveyor surface, and operable 'to rmlyigripand resilientl'y tension the tread stock .during severance thereof by an associated .cutting instrumentality:wherebythe stock is vdrawn away from the cutting instrumentality immediately upon:passage thereof through the stock, thereby preventing unnecessary 'contact of the rubber stock with the `cutting instrumentality after -sevarance has been effected.

MIt is fur-ther 'object vof "this u invention to -pro- -vide improved vrm'ethods vvfor cutting tire tread stock, Lor-similar -flexible sheet stock, -by yiirmly 9l claimsl (c1.v 164.46)

holding the same-under elastic ltensionduring :the passageof a cutting instrumentality there through, Lwherebyithe severed 'portion of 'stocklis immediately freed from contact withthe .cutting instrumentality, .and completely partedtfrom the remaining lbody portion :of lthe fstock.

.ltlis still another object. of :this invention :to provide apparatus "of the 'character described, `Whose `function is controlled eiciently land :eco- Inominally :through theuse .of vacuumproducin`g `means ihaving. associated therewith relati-velyzrsimple,:yet eilicient valve'controls. i

For f a furtherand.l more detailed understandingfofrthe presentinventionfand the various ad? ditional objects .and `advantages thereof, refer` `ence is made;` to l:thefollowingdescription .and the accompanying'drawin'gs wherein:

Fig. 11 is 4a .siderelevational view ofca treadicut- 'ting machine formedinaccordance Withthetpress ent invention;

Fig. 2 is a top plan View thereof; l vvFig.v 3 Vis an ienl'arged vertical 'sectional `View ,taken alonglthe line f3-3 vof"1iig.:1;

yFig. 4 is an .enlarged-',.detailed'sideselevational Vvievv :of the vpresent "tread-'cutting machine, `looking ,toward (the 'vacuum-control system thereof.;

Fig. 5 `is anfenlargedfragmentary-horizontal `sectional Zview 'taken through the vpresent .machine direc'tlyl above the :associated conveyo'rf'bed and interposed vacuum hold-down f. plates Fig. `6 isa fragmentary fvertical sectional'view itaken along -the 1ine'6,-46offFig.f5;

VFig. 7 isan :enlarged fragmentary-side elevational View, partiallyinverticalfsection, of one fof the vacuum l hold-downl plates 'and its associated 4pressure connection; 3.

Fig. 8 is a plan viewfof the control systemfemtbodied in theipresent machine, and' disclosingthe associated :valve members in `vertical cross-sec tOn; Fig. 49,:is a verticalV sectional view* taken'alon'g the line .9-9 of Fig. 8;

Fig. 10 is an enlarged vertical sectional yview taken through the frelatively separable Y'vacuum hold-'down iplates, `and disclosing their 'aoperating relation :to the Vassociated "rotary -cutting -fblade and treadzstock;

y Fig. r11 is aidiagrammaticillustrationof a-modineel form orco'n'trol mechanism which `may-be utilized -inias'sociation `witlifth'e fpresent treadf'cutting machine; l

fFig.'-`12 is adetaile'dvertical-sectional vievvt'a'ken throughfaivalve'off theztype embodiedfinf the modi# ned 'control mechanism-disclosedin Fig. 1li. -neferringfnowfto theldrawingsfthe numeral 1S enclosed channel member 32.

generally designates an elongated angle iron frame which advantageously may form a continuation of a complemental frame I6 which is provided upon its upper surface with a plurality of anti-friction rolls I1 which serve to convey a continuous sheet of extruded tread stock I8 away from the associated extrusion machine. The frame I is provided with a plurality of vertical side members between which are supported a liquid-holding trough or tank I9 through which the continuous sheet of tread stock passes for cooling after initial extrusion. From the tank, the sheet stock I8 is directed, by means of a continuous conveyor belt 20 backwardly across the frame i5, with the free end thereof being manually placed longitudinally upon a relatively elevated conveyor bed 2| which also comprises a plurality of anti-friction rolls 22. The conveyor bed 2i is carried upon the upper portion of the base frame I5, in vertically spaced relation to the conveyor belt 20, in order to provide sufficient clearance for the passage of the tread stock upon the continuous belt conveyor 20 beneath the conveyor bed.

Arising vertically upward from'the base frame I5 is a superstructure or head frame 23 which extends across the conveyor bed 2l. The superstructure 23 is provided with a pair of inwardly directed channel members 24 in which are slidably positioned a pair of anti-friction rolls or wheels 25 carried by a transversely movable motor bracket or carriage 26. Supported in a diagonal position upon the carriage 26 is an electric motor 21 which directly drives a circular cutting knife 28 disposed in acutely angular relationship to the plane of the conveyor bed 2I. The carriage 28 is provided with an outwardly extending handle 29 by which the entire carriage, motor and knife may be manually moved transversely across the conveyor bed during cutting operations.

Interposed within the conveyor bed 2I, between a pair of adjacent'anti-friction rolls 22, and-,extending transversely thereof, is a rst stationary vacuum-hold-down'plate 30 which is provided-at its upper surface with a perforate relatively horizontal head plate 3I and an integral The perforations ofthe vacuum hold-down plate 30 comprise a plurality of relatively closely spaced and countersunk openings 33 which open toward the upper surface of the conveyorbed, and communicate interiorly of the plate with an enclosed chamber 34. Also communicating with the chamber 34 is a vacuum and pressure supply line 35 which extends -outwardly beneath the conveyor bed 2I to one side thereof.

Disposed in longitudinally spaced relation to the stationary hold-down plate 30`is a second similarly formed hold-down plate 36 which is provided at either end with a pair of supporting and depending brackets 31 which, in turn, are pivotally mounted, as at 38, to the side members of the frame I5 in a manner to permit of relatively limited pivotal rocking movement thereon.

vPivotally linked with the intermediate portion of one of the brackets 31, is the outer end of a pistonv rod 33 extending vexteriorly of a suctionactuated ram 40. Also connected with the bracket 31, opposite the piston rod 39 of the ram, is a contractile spring 4I which functions to hold the bracket and the associated hold-down plate against relative separating movement with respect to the stationary plate 30. The suctionactuated ram 40 operates-in response to subat- 4 mospheric pressures established therein to impart outward separating movement to the second plate 36 with respect to the stationary plate 30, in order to increase the normal longitudinal spacing between the two hold-down plates.

As shown particularly in Fig. '10 of the drawings, the normal spacing between the two vacuum hold-down plates provides a transversely extending knife passage 42 through which the outer peripheral portion of the rotary cutting blade 28 may pass upon transverse movement thereof with respect to the conveyor bed 2l. Communicating with the underside of the movable hold-down plate 36, is a hose connection 43 which, in turn, is connected with the outer end of a flexible conduit 44 extending beneath the conveyor bed 2I and outwardly to one side of the upper frame or super structure 23.

The outer end of the hold-down plate conduits 35 and 44 are .provided with elbow joints 45 which provide vertically upward continuations of the conduits, and communicate with the lower side of a pair of two-way diaphragm-type valves 46 and 41. The opposite connections of the valves 46 and 41 are provided with vacuum-supply lines 48 which extend upwardly of the superstructure 23 and terminate in a common manifold 49. It will be understood, that the manifold 49 is connected with a central vacuum-supply line 49a which is coupled with a suitable remotely disposed fluid-displacement pump, not shown. Each of the diaphragm-type valves embody a sliding spool or gate 50 which is provided with a vertically extending channel 5I which, in response to movement of the spool 59, may be brought into and out of registration with the vacuum supply line 48, and the upward extension of the hold-down plate conduits 35 and 44. The movement of the spool 59 is controlled through the operation of a flexible diaphragm 52 which is enclosed within a suitable elliptical housing 53, and which is responsive to fluid pressure introduced in one side of the housing through a uid supply line 54. The diaphragm 52 and the associated spool valve 59 are integrally joined by a connecting rod 55 around which is disposed a coil spring 56 which functions to normally hold the spool valve 50 in a closed position with respect to the registering conduits 48 and 44. In operation, each of the diaphragm valves function in response to superatmospheric pressures exerted upon the diaphragm face to move the spool valve 59 into registration with the vacuumsupply line 48 and theV respective hold-down conduits, in order that sub-atmospheric pressures may be established within each of the hold-down plates.

The operation of the suction-actuated ram 40 is controlled in a similar manner by an identical valve 51 which is connected with a third branch or the vacuum-supply manifold 49, and with a conduit communicating with the ram 49. Each of the fluid-supply lines 54 communicating with the respective valves, are joined by a common manifold 58 which, in turn, is connected with a single fluid pressure supply line 59 in which is interposed a three-way valve Si! which provides for the introduction of superatmospheric pressure within the respective diaphragm valves, and for the exhausting of superatmospheric pressures therein. As shown particularly in Fig. 8 of the drawing, the valve 60 is formed with an inner rotatable spool or core 6I in which is formed a three branch channel 62 which, upon proper rotation of the core 6I will bring lvalves and associated lines -to be vexhausted v'through an'eXha-ust opening 63 -formed infthe lsurefsupplylineii. The movement-of the core `o1' ispool-'6| `is controlled by means of a leverf @64.carried vexteriorly of the valve casing, `and "spring-pressed, as at 64a, kso as to assume a "position normally permitting ofthe entrance or passage of pressure to each of the valves. The

operation of the lever 64 is controlled-by Amove ment of ltheknife carriage 26 rwhichis provided with an outwardly extending bracket 65-f0rfen gagement with the upper end of the trip lever l64. `In loperation, when lthe knife and its associated carriage 26 occupies a normal position l'of rest to one side of the'conveyor bed as showniin Fig. .3cr the drawings, the bracket 65 Will-hold fthevalve lever 64 in a closed position preventing the entrance of fluid under pressure withinthe pressure supply linesv 54 and the associated di- Iaphragm valves. Conversely, as thekni'fe'and its carriage are drawn transversely across the conveyor bed andl out of engagement with the valve lever '64, 4the same will move under spring tension to Ianfopen position permitting the entrance of uid under pressure within the respective :pressure supply lines and the associated diaphragm valves, to open the same thereby permitting communication between the vacuum- `supply line Y48 and the hold-down conduits 35 `and 44, to `establish subatmospheric pressures within the respective hold-down plates, and to actuate the ram 4l) to cause relative separating movement between the two hold-down plates. In the above outlined operation, it has been `found vadvantageous to retard. the action of kthe `ram "4D `in 4vseparating the two plates, with respect to the application of vacuum therein. Toward this end, the pressure supply line associated vwith the ram-controlling diaphragm valve '51 is `provided with an interposed check valve 66 fwhich retards the action of the valve 51 until 'the remaining valves 30 and 41have completely opened to establish subatmospheric pressures within the v'hold-down plates, at which time pressuremay Ibe introduced within the valve 51 per- `'ixlitting `operation vof the ram 40 kto movey 'the second hold-down plate relative to 'the lstationary plate :30.

AIt will thus be seen, that a sheet of tread stock 'carried upon the conveyor` bed 2| in spanning relation "to the two hold-down plates 30 and 36, ilrst be subjected on either side of the knife passage 4-2 to vacuum pressures tending to Vclamp the tread stock firmly to each ofthe hold-down plates, and afterwards, due to the relative 'sep- '.arating movement of the movableplate, the tread stock will be resiliently tensioned, and `Slightly stretched across the knife passage 42 prior to the passage of the rotary cutting blade 28 across the conveyor bed and through the ltread stock. 'It will here -be understood, that :the operation of the various vacuum-creating l 'stationary plates.

ofthe stock, `that portion held by the movable vacuum hold-down plate will be immediately zwithdrawn from contact with the knife blade 28. This action is particularly illustrated in de tail in Fig. 10`of the drawing.

Advantageously, the present apparatus may be'provided with a blow-back system which functionsto momentarily discharge a blast of compressed air within each of thev vacuum hold-down plates'and rthe ram et, in order to abruptly disengage 'the severed portions of strip stock from the plates, and additionally to relieve the vacuum pressurewithin the ram 4Q, to allow the Same to return to its position of rest, and permitting the movable hold-down plate to once again return to its normal position in spaced relation to the Figs. 3 and 8 of the drawings Aillustrate one system `which may be adapted for this `purpose, in conjunction with the previously outlined fluid pressure system. The respective conduits leading to the ram 4S, the stationary hold-down plate 35, and the movable hold-down plate 36 are joined below the diaphragm valves by a common manifold conduit G1 in which is interposed a single compressed air supply conduit 68 leading from a diaphragm type valve 69, of somewhat similar structure to the diaphragm valves previously outlined. The valve structure 69 diiers from the previously outlined valve in that the same is provided with a slidable spool or gate l which is formed with a single passage 'H for registration with the supply line 5t, and additionally with a relatively enlarged passage or chamber l2 permitting of simultaneous registra* tion with a compressed air tank outlet'l'S, anda compressed air inlet line or conduit "i4, The gate 10 of the valve '69 is responsive to the movement of a iiexible diaphragm and associated push rod l5 which in turn, is actuated by fluid pressure in troduced within the valve through an extension conduit 'i6 which is tapped into one of the three branches of the iluid pressure supply line 59, whereby pressure is supplied to the valve 69 simultaneously with the other diaphragm valves upon operation of the cutting knife. As shown in Fig. 8 ofthe drawings, the spool or gate E53 of the valve 59 normally occupies a position permitting of communication between the compressed air tank outlet 'i3 and the pressure supply line 68. In response to pressure acting through the iiuid pressure system 58 upon the diaphragm of the valve 69, the gate is moved downwardly to close the conduit 6i?, and. to open the tankoutlet 'f3 to the incoming compressed vair supply line 74, in order that the tank maybe initially charged with compressed air at the time .the hold-down plates and ram are being subjected to subatmospheric operation. As the knife yreturns `from its cutting operation to itsl normal position ofrest to one side of the conveyor bed, with the bracket E5 engaging the valve lever S4,

pressure .is released upon the valve `69 to return tem are relatively small, and are maintained with suilicient force only to initially puff the sheet stock away from the perforations of the holddown plate, thereby speeding the overall cutting operation, and returning the machine to a normal condition for another cycle of operation.

' Figs. ll and l2 of the drawings disclose a modified type of control system utilized to control the action of the hold-down plates 3i) and 3% and the suction-actuated ram A@ in response to the movement ci the cutting blade and its associated carriage. This modied system utilizes a three-way, three position, Y-valve El@ which is connected with the two hold-down plates and the ram it by a three-branch conduit 8i. The valve 8G is oonstructed with an inner rotatable spool 82 in which is formed a Y-shaped channel 83. Positioned for separate registration with the channel B3 are three conduit connections 84, S5 and 35. The conduit 8! is connected with the valve at connection 85, and the remaining connections 34 and 85 are coupled respectivel5T with a compressed air supply line S? and a vacuum supply line SS. The valve is provided with an external and laterally oiset operating lever 89 which controls the position of the spool 82. The operating lever 8S is spring-pressed to a position permitting or" comn munication between the vacuum supply line 3S and the conduit t! leading to the hold-down plates and ram, 'whereby subatmospheric Ipressures may be established therein. In addition, the lever is movable against spring tension to positions providing communication between the compressed air supply line and the conduit 8i, and a neutral position closing all three connections. The movement of the valve lever 85 is controlled by an extension de which is carried by the blade carriage 26 above and in the vertical plane of the lever. The extension is provided with a pair of spaced depending latches di and 92 which serve to engage the upper portion or the lever during different stages of travel of the extension. The latch Qi is rigidly carried by the extension, and merely acts as a stop for the lever,

awhile the other latch Q2 is mounted on the extension, in the manner of the common door latch,

for spring tensioned swinging movement in one direction only. The swinging latch 92 is positioned toward the outermost end of the extension 90 and is arranged swinging movement inwardly of the extension when the carriage and cutting blade are moved from their normal position of rest to one side of the conveyor bed and across the same.

In operation, with the carriage and extension f occupying a rest position to one side of the conveyor bed, the operating lever 89 is held in a neutral position by the latch 9|, thus preventing the establishment oi either sub or superatmospheric pressures within the plates and ram. As

Athe carriage and extension are moved outwardly across the conveyor bed, the rigid latch 9! is drawn out of engagement with the lever 89 permitting the same to move under spring tension to a position establishing communication between the vacuum supply line 8S, and the hold-down plates 363 and 3E and the ram Mi.

gages the upper portion of the valve lever and swings the same in an arcuate path to a position establishing communication between the compressed air line 8l and the hold-down plates and ram. At this position, further movement of the carriage and extension toward their position of rest causes the latch S2 to ride over the upper end of the lever, due to the arcuate movement thereof, and permits the lever to snap back under spring tension to a neutral position in engagement with the stop latch 9|. It will thus be seen, that the opening of the compressed air supply line 8l to the plates and ram is only momentary as the extension and blade carriage return to their position of rest. This momentary opening of the compressed air line causes the partial vacuum within hold-down plates and ram to be relieved and additionally exerts a small blow- .back pressure upon the severed end portions of the tread stock to initially free the same from contact with the hold-down plates.

In the actual operation of the machine, the free end portion of the continuous sheet of uncured tread stock I8 is manually directed upon the conveyor bed 2l simultaneously with the operation of the continuous conveyor belt 20. The free end portion is then slid longitudinally of the bed 2| until engagement is made between the end edge of the stock and a longitudinally adjustable stop device 93 which is carried by the frame I5 in predetermined longitudinally spaced relation to the plane of movement of the cutting blade 28. Thus a definite and predetermined length of stock is obtained between the blade and stop device, which length corresponds to that desired for the tread of a given size of pneumatic tire. At this time, the cutting blade and carriage are moved out of their rest positions to establish sub-atmospheric pressures within the hold-down plates 39 and 36, causing the tread stock to be rmly gripped, and within the ram 46 to cause separating movement of the movable plate 36 and to elastically tension the tread stock between the two plates. The tread stock is then severed cleanly between the two plates upon complete transverse movement across the conveyor bed. The cutting blade and carriage are then moved backwardly across the bed to their rest positions to momentarily operate the blow-back system to free the severed ends of tread stock from the plates. The cycle of operation is then repeated with respect to the next length of tread stock until the continuous sheet has been entirely severed into a multiplicity of strips of predetermined length.

In view of the foregoing, it will be seen that the present invention provides eiilcient apparatus and methods for cutting uncured normally thick and relatively flexible tire tread stock into strips of uniform and predetermined lengths. Machines formed in accordance with the present invention are characterized by their ability to cut tread stock evenly and smoothly without benet of water lubrication and ambient elaborate equipment. Such machines greatly reduce the number of operators normally required during cutting operations carried out with previously known machines of this type. Particularly, machines embodying the present invention are characterized by their ease of operation, their economy of maintenance and operation, and their mechanical efficiency.

While certain preferred embodiments hav been disclosed in detail, it will be understood that various changes as to constructional details may beA eiiectedxwithout` departingv from the spirit of the present .inventionxas-.dened by the following claims.

i Ilclaim:

1. Apparatus' for cutting relatively flexible sheet stock comprisinga conveyor bed for the sliding reception of sheet stock introduced longitudinaliy` thereon,4 apair of spaced relatively movable perforate. suction .members ydisposed transverselyof and withinthe plane ofsaid conveyo1' bed;said suction members being operable in response to subatm'ospheric pressures established therein to rigidly hold sheet stock positioned upon said conveyor bed and spanning said members, andy uponlrelative separating movementftotensionsuch. stock Vbetween said members; a cutting device movable across saidcon'- veyor bed..betweenl..said'"suction members and operable to sever sheet stocklheld under tension by the latter, and means-responsiveto the movementpi'fsaidrcutting device -fjor` establishing subatmospheric pressures withinsaid members and for imparting relative separating movement thereto.

2. .Apparatus for cutting relatively vflexible sheetstock comprising.-aconveyor bed for the sliding reception ofsheet stock introduced longitudinally thereon, a. pairlofl spaced relatively movable perforate suction members disposed transversely of and within the plane of said conveyor bed; said suction members being operable in response to subatmospheric pressures established therein to rigidly hold sheet stock positioned upon said conveyor bed and spanning said members, and upon relative separating movement to tension such stock between said members; a cutting device movable across said conveyor bed between said suction members and operable to sever sheet stock held under tension by the latter, and means responsive to the movement of said cutting device for establishing subatmospheric pressures within said members and for imparting relative separating movement thereto, said last named means including a vacuum-actuated ram connected with one of said suction members and operable to move the latter relative to the other 'of said members, a vacuum line communicating with said suction members and said ram, and a valve operable by said cutting device to alternately open and close said vacuum line.

3. Tin a machine for cutting sheet stock, a conveyor bed for the sliding reception of sheet stock introduced longitudinally thereon, a pair of relatively separable suction members interposed within said conveyor bed and extending transversely thereof, said members being operable to hold and tension sheet stock positioned on said conveyor bed and extending across said members upon establishment of subatmospheric pressures therein and upon relative separating movement, a cutting device carried above said conveyor bed for movement across the same and between said suction members, said cutting device being operable upon such movement to sever sheet stock held and tensioned by said members, and means responsive to the movement of said cutting device for establishing subatmospheric pressures within said suction members and for effecting relative separation thereof.

4. Apparatus for cutting flexible sheet stock comprising a frame provided with a longitudinally extending conveyor surface for the sliding reception of relatively exible sheet stock, a pair of spaced and relatively movable perforate suctionplatescarriedi by saidV frameand inter-2 posedftransversely` within-.the plane of said con. veyor surface, the spacing between said plates providing a passageway extending transversely through the plane of said vconveyor surface, a cutting device carried by saidjframe for moves' ment across said conveyor'surface, said cutting device extending within the passageway between said plates andoperable upon movement across said conveyor surface to yseversheet stock positioned thereon and spanning said suction plates.' suction-actuated means carried by said frame for imparting'relative separating movement to said suction plates, a suction line communicating with said suction plates and with said suctionaictuated'means,` andvalve means Vassociated with said suction `line-andresponsiveto the movement of said cutting. device: forl openingnand closing Said suction line to' saidv suction plates andsaid suction-actuated means.I i i l' f 5. In apparatus for` cutting tire tread'. vstock into'l strips ofpredetermined'length, a conveyor bed including aA .pluralityof transversely "diss-z posed antifriction roll-s for thesliding reception of tread stock introduced: 'longitudinally thereon, a" first stationary perforate suctionI platerinter-e; posedv transversely awithin.V said conveyorbe'cl between a pair of said. anti-friction rolls, .a second relatively-movable perforate suctionplate disposed in longitudinally spaced relation to said rst suction plate and dening therewith a transversely extending knife passage, a rotary cutting knife arranged for transverse movement across said conveyor bed between said suction plates, means communicating with said suction plates for establishing a partial vacuum therein, whereby tread stock positioned on said conveyor bed and spanning said plates may be held by suction against the latter, and means connected with said movable suction plate for imparting separating movement thereto with respect to said stationary plate, whereby tread stock held by suction against said plates may be resiliently tensioned prior to cutting by said knife.

6.. In apparatus for cutting tire tread stock into strips of predetermined length, a conveyor bed including' a plurality of transversely disposed antifriction rolls for the sliding reception of tread stock introduced longitudinally thereon, a first stationary perforate suction plate interposed transversely within said conveyor bed between a pair of said antifriction rolls, a second relatively movable perforate suction plate disposed in longitudinally spaced relation to said rst suction plate and defining therewith a transversely extending knife passage, a rotary cutting knife arranged for transverse movement across said conveyor bed between said suction plates, means communicating with said suction plates and responsive to the transverse movement of said knife for establishing a partial vacuum within said plates, whereby tread stock positioned on said bed in spanning relation to said plates may be held by suction thereto, and' means connected with said movable suction plate and responsive to the movement of said knife for imparting limited separating movement thereto' with respect to said stationary plate, whereby tread stock held by said plates may be resiliently tensioned prior to cutting by said knife.

'7. In apparatus for cutting relatively flexible sheet stock, a conveyor bed for the sliding reception of sheet; stock introduced longitudinally thereon, a1 pairv of spaced and relatively movable vacuum hold-down plates interposed within said conveyor bed and extending transversely thereof, said plates being operable in response tov sub atmospheric pressures established therein to rigidlyholdsheet stock received on said conveyor bed and spanning said plates, and upon relative separating movement to tension such stock between `saidl plates, a cutting device arranged abovesaid conveyor bed for movement trans versely Ythereof between said plates, means connected with one of said plates for imparting relative separating movement thereto, and means communicating with each of said plates for alternately establishing subatmospherio and superatn'iospheric pressures therein. Y

8, In Eapparatus'for cutting relatively flexible sheet stock, a conveyor bed for'the sliding receptionof sheet stock introduced longitudinally thereonga pair of spaced and relatively movable vacuum hold-down plates interposed within said conveyor bed and extending transversely thereof,'said plates being operable in response to subatmospheric pressures established therein to rigidly hold sheet stock received on said conveyor bed and spanning said plates, and upon 25 connected With one of said plates for imparting relative separating movement thereto, and means communicating with each of said plates for alternately establishing subatmospheric and superatmospheric pressures therein, said lastnamed means being operable in response to the transverse movement of said cutting device.

9. The method of cutting tire tread stock which comprises bridging an intermediate por-Y tion of the stock between supports, anchoring the stock on either side of its bridging portion to the supports by Vacuum pressures applied to the support-contacting surfaces thereof, placing the bridging portion of the stock under elastic tension, and thereafter cutting the said stock along the bridging portion thereof While under elastic tension.

' VANCES. FIRESTONE.

REFERENCES CITED v The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,758,729 Wilson May 13, 1930 2,429,944 Rayburn et al Oct. 28, 1947 ,2,429,945 Rayburn Oct. 28, 1947 

